TanDEM-X - Radar Interferometry with unprecedented Accuracy in close Formation Flight with TerraSAR-X Satellites

The German Aerospace Center DLR is funding a study of a radar satellite system - TanDEM-X - for mapping the Earth's topography with unprecedented precision. TanDEM-X consist of two high-resolution imaging radar satellites forming a huge radar interferometer capable of measuring terrain topography with 2 m accuracy, surpassing anything available today. TanDEM-X will generate digital maps from any part of the world for a wide spectrum of research topics, as well as for commercial exploitation and security applications.

TanDEM-X Artist's impression / © EADS Astrium

The TanDEM-X main mission objective is to generate Digital Elevation Models (DEM's)

• on a global scale with unprecedented quality and timeliness
• for outstanding geoscientific research and commercial applications

TanDEM-X is a national SAR interferometry mission employing

• the TanDEM-X satellite as a rebuild of TerraSAR-X1 (TSX-1) with mission upgrades
• TSX-1 to form the tandem constellation, being continued with privately funded TSX-2

The TanDEM-X mission, proposed for launch in 2008 provides

• a first to market position in high resolution DEM's
• global coverage in 3 years and long term update services
• a German lead position in novel SAR missions, concepts and bistatic radar techniques

The TanDEM-X mission is an evolution capitalizing on technology and experience from

• SRTM (interferometry)
• GRACE (orbit determination accuracy, formation flying, low cost approach)
• TerraSAR-X (active phased array SAR)

The study with a duration of 9 months will be managed by EADS Astrium GmbH as prime contractor to DLR. Dedicated tasks are subcontracted to DLR-HR, GeoForschungsZentrum-Potsdam and InfoTerra GmbH. DLR-HR will also coordinate the scientific aspects of the mission.

TanDEM-X - Radar Interferometry with unprecedented Accuracy in Formation Flight with TerraSAR-X Satellites

The TanDEM-X (TerraSAR-X add-on for Digital Elevation Measurement) mission has the primary goal to generate a global Digital Elevation Model (DEM) with unprecedented accuracy, corresponding to the DTED 3 specifications. This goal will be achieved by means of bi-static SAR imaging using a tandem formation of SAR satellites, created by TerraSAR-X and a second satellite - TanDEM-X. Once the useful lifetime of TerraSAR-X is expired the TanDEM-X mission can be continued with the second model of the TerraSAR-X Public-Private Partnership series, TerraSAR-X no. 2.

Large Area Mapping of TanDEM-X of the TanDEM-X satellite system in orbit / © EADS Astrium

The TanDEM-X satellite will be designed for 5 years in orbit lifetime and will have SAR system performance features which are almost identical with TerraSAR-X. This will allow not only operation in a mono-static mode, independent from TerraSAR-X, but in a bi-static mode, i.e. synchronized with TerraSAR-X.

Currently a TanDEM-X Phase A study is being performed under EADS-Astrium lead which will be finished in June 2005 with a proposal for the following project phases. It is hoped that this proposal will be accepted by DLR , and a contract will be awarded in fall 2005, aiming at a TanDEM-X launch in late 2008.

The TanDEM-X Phase A work will mainly focus on the challenging and schedule driving aspects of the mission. This covers e.g. the analysis and definition of SAR techniques for the new interferometric modes, the derivation and detailing of design adaptations required on TerraSAR-X and the minor modifications of the TerraSAR-X design needed for the TanDEM-X satellite.

Furtheron the highly challenging close formation flight will be analysed in detail and it's feasibility will be demonstrated. A comprehensive survey of the potential scientific and commercial fields of application will be undertaken to establish the user requirements. Based on their evaluation and ranking, a "best fit" set of mission requirements will be derived taking into account boundary conditions like the financial budget, the existing TerraSAR-X design and schedule and any technical limitations.

In a compact effort Industry and DLR Institutes will derive detailed design concepts for space and ground segment in preparation of a committing Phase B, C/D, E proposal. The commercial potential of the TanDEM-X mission will be assessed and the related business case will be established.

TanDEM-X Mission Goals

The main goal of the TanDEM-X mission is the generation of world-wide, consistent, timely, high-precision Digital Elevation Models (DEM, <12m posting and <2m height accuracy) as basis for a wide range of scientific research, as well as for operational, commercial DEM production. Further mission goals are:

TanDEM-X Mission Concept / © EADS Astrium

New applications based on velocity measurements with along-track interferometry (ATI) Stimulation of innovative SAR techniques in bi-static measurement configuration Development of close formation flying technology being a basis for many future missions Achievement of a first to market position for a coherent, global standard, high quality DEM service Achievement of a long term availability of X-Band data for scientific and commercial users, ensuring a sustainable product development and data delivery

TanDEM-X System Characteristics

TanDEM-X will have the following system characteristics:

• Polar synchronous orbit at 514 km, 11 days repeat cycle
• Close formation flight of TerraSAR-X and TanDEM-X
• Full global coverage
• DEM's in DTED-3 quality
• Operation in
  • bistatic and monostatic InSAR configuration
  • Stripmap, Scansar and Spotlight modes
  • Full polarisation (Mono, Dual, Quad)
  • Moving Target Detection
  • Right / left looking orientation for optimisation of revisit period
• Quasi realtime data downlink at 300Mbps, up- and downlink encrypted
• Onboard mass memory capacity > 256
• Dual frequency GPS receiver for precise baseline determination
• Inter Satellite Link for RF phase synchronisation and autonomous formation control

The TanDEM-X Satellite provides resources for a secondary payload, see download of Announcement of Opportunity (AO) for Secondary P/L below.

TanDEM-X Poster (4694 Kb)

TanDEM-X AO for 2nd P/L (684 Kb)